#include<bits/stdc++.h>
#define int long long
using namespace std;
int pos[205],t[205];
int dp[205][205][205][2];
int inf=1e9+5;
int n,l;
int g(int i,int j){
if(i==n+1)i=0;
if(j==n+1)j=0;
return min(abs(pos[i]-pos[j]),l-abs(pos[i]-pos[j]));
}
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cin>>n>>l;
for(int i=1;i<=n;i++)cin>>pos[i];
for(int i=1;i<=n;i++)cin>>t[i];
for(int i=0;i<=n+1;i++)for(int j=0;j<=n+1;j++)for(int k=0;k<=n+1;k++)dp[i][j][k][0]=dp[i][j][k][1]=inf;
dp[0][n+1][0][0]=dp[0][n+1][0][1]=0;
int ans=0;
for(int i=0;i<=n;i++)for(int j=n+1;j>=1;j--)for(int k=1;k<=n;k++){
if(j<=i)continue;
if(i+n-j+1<k)continue;
if(i==0&&j==n+1)continue;
//0
if(i>0){
dp[i][j][k][0]=min(dp[i-1][j][k][0]+g(i-1,i),dp[i-1][j][k][1]+g(i,j));
int tme=min(dp[i-1][j][k-1][0]+g(i-1,i),dp[i-1][j][k-1][1]+g(i,j));
if(tme<=t[i])dp[i][j][k][0]=min(dp[i][j][k][0],tme);
}
//1
if(j<n+1){
dp[i][j][k][1]=min(dp[i][j+1][k][0]+g(i,j),dp[i][j+1][k][1]+g(j+1,j));
int tme=min(dp[i][j+1][k-1][0]+g(i,j),dp[i][j+1][k-1][1]+g(j+1,j));
if(tme<=t[j])dp[i][j][k][1]=min(dp[i][j][k][1],tme);
}
if(min(dp[i][j][k][0],dp[i][j][k][1])<inf){
ans=max(ans,k);
//cerr<<"can:"<<i<<' '<<j<<" "<<k<<':'<<dp[i][j][k][0]<<" "<<dp[i][j][k][1]<<"\n";
}
}
cout<<ans;
}
